Stevia (scientific name: Stevia rebaudiana) comprises sweetness components having approximately 300 times the sweetness of sucrose. The known sweetness components in stevia include stevioside, rebaudioside A, rebaudioside C, rebaudioside D, rebaudioside E and dulcoside A. Of these, rebaudioside C and dulcoside A are known to also have a strong bitter taste.
Stevia extracts containing these sweetness components, when used as sweeteners, have the disadvantage of producing unpleasant tastes such as bitterness as residual aftertastes. Examples of stevia sweeteners with improved taste quality that are known include stevia sweeteners with increased rebaudioside A content, and transglucosylated stevia sweeteners prepared by α-addition of glucose on the aforementioned sweetness components (Patent documents 1 and 2, for example).
Also, Patent document 3 teaches that the aftertaste, bitterness and metallic taste of transglucosylated stevia sweeteners is reduced by adding flavor improvers, containing sugarcane-derived extracts and specific auxiliary additives, to transglucosylated stevia sweeteners.